The invention relates to the use of polyfluoro copolymers as coatings for implantable surgical medical devices.
Implantable medical devices are used in various medical procedures. Such devices include, without limitation, stents, catheters, sutures, meshes, vascular grafts, shunts and filters for removing emboli.
Stents, which generally are open tubular structures, have become increasingly important in medical procedures to restore the function of body lumens. Stents now are commonly used in translumenial procedures such as angioplasty to restore adequate blood flow to the heart and other organs. However, deployment of stents may stimulate foreign body reactions thereto that result in thrombosis or restenosis.
To avoid these complications, a variety of stent coatings and compositions have been proposed to reduce the incidence of these complications. The coatings may be capable themselves of reducing the stimulus the stent provides to the injured lumen wall, thus reducing the tendency towards thrombosis or restenosis. Alternately, the coating may deliver a pharmaceutical/therapeutic agent or drug to the lumen that reduces smooth muscle tissue proliferation or restenosis. The reported mechanism for delivery of the agent has been via diffusion of the agent through either the bulk polymer, or through pores that are created in the polymer structure, or by erosion of a biodegradable coating.
Both bioabsorbable and biostable compositions have been reported as coatings for stents. They generally have been polymeric coatings that either encapsulate a pharmaceutical/therapeutic agent or drug, e.g. taxol, rapamycin, etc., or bind such an agent to the surface, e.g. heparin-coated stents. These coatings are applied to the stent in a number of ways, including, though not limited to, dip, spray, or spin coating processes.
One class of biostable materials that has been reported as coatings for stents is polyfluoro homopolymers. Polytetrafluoroethylene (PTFE) homopolymers have been used as implants for many years. These homopolymers are not soluble in any solvent at reasonable temperatures and therefore are difficult to coat onto small medical devices while maintaining important features of the devices (e.g. slots in stents).
Stents with coatings made from polyvinylideneflouride homopolymers and containing pharmaceutical/therapeutic agents or drugs for release have been suggested. However, like most crystalline polyfluoro homopolymers, they are difficult to apply as high quality films onto surfaces without subjecting them to relatively high temperatures, e.g. greater than about 125-200xc2x0 C., that correspond to the melting temperature of the polymer.
It would be advantageous to develop coatings for implantable medical devices that will reduce thrombosis, restenosis, or other adverse reactions, that may include, but do not require, the use of pharmaceutical or therapeutic agents or drugs to achieve such affects, and that possess physical and mechanical properties effective for use in such devices, even when such coated devices are subjected to relatively low maximum temperatures.
The present invention includes biocompatible coatings and films for use on implantable medical devices and medical devices comprising such coatings and films applied to a surface thereof that is to be in contact with body tissue of a mammal. The biocompatible film provides an inert surface to be in contact with body tissue of a mammal upon implantation of the device in the mammal. The coating and film comprise a film-forming polyfluoro copolymer comprising the polymerized residue of a first moiety selected from the group consisting of vinylidenefluoride (VDF) and tetrafluoroethylene (TFE), and the polymerized residue of a second moiety other than said first moiety and which is copolymerized with said first moiety, thereby producing the polyflouro copolymer, said second moiety being capable of providing toughness or elastomeric properties to the polyfluoro copolymer, wherein the relative amounts of said polymerized residue of said first moiety and said polymerized residue of said second moiety are effective to provide the coating and film produced therefrom with properties effective for use in coating implantable medical devices.